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CONTANT
1.
Computer
-
Home
2.
Computer
-
Overview
3.
Computer
-
Applications
4.
Computer
-
Generations
5.
Computer
-
Types
6.
Computer
-
Componen
ts
7.
Computer
-
CPU
8.
Computer
-
Input Devices
9.
Computer
-
Output Devices
10.
Computer
-
Memory
11.
Computer
-
RAM
12.
Computer
-
Read Only Memory
13.
Comp
uter
-
Motherboard
14.
Computer
-
Memory Units
15.
Computer
-
Ports
16.
Computer
-
Hardware
17.
Computer
-
Software
18.
Computer
-
Data and Information
19.
Computer
-
Networking
20.
Computer
-
Operating System
21.
Computer
-
Internet and Intranet
22.
Computer
-
How to Buy?
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Computer Fundamentals Tutorial
Computer is an advanced electronic device that takes raw data as an input from the user
and processes it under the control of a set of instructions (called program), produces a
result (output), and saves it for future use. T
his tutorial explains the foundational
concepts of computer hardware, software, operating systems, peripherals, etc. along
with how to get the most value and impact from computer technology.
Audience
This tutorial has been prepared for beginners as well as
advanced learners who want to
deal with computers. The tutorial is also very useful for undergraduate students of
computer science, engineering, business administration, management, science,
commerce and arts, where an introductory course on computers is
a part of curriculum.
After completing this tutorial, you will find yourself at a moderate level of expertise in the
knowledge of computer basics from where you can take yourself to the next level.
Prerequisites
Knowledge of computers is not a prerequisite
to follow the contents of this tutorial. This
tutorial assumes no background in Computers or Computer programming.
Computer
-
Overview
Today’s world is an information
-
rich world and it has become a necessity for everyone
to know about computers. A comput
er is an electronic data processing device, which
accepts and stores data input, processes the data input, and generates the output in a
required format.
The purpose of this tutorial is to introduce you to Computers and its fundamentals.
Functionalities of
a Computer
If we look at it in a very broad sense, any digital computer carries out the following five
functions −
Step 1
− Takes data as input.
Step 2
− Stores the data/instructions in its memory and uses them as required.
Step 3
− Processes the data and
converts it into useful information.
Step 4
− Generates the output.
Step 5
− Controls all the above four steps.
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Advantages of Computers
Following are certain advantages of computers.
High Speed
Computer is a very fast device.
It is capable of performing
calculation of very large amount of data.
The computer has units of speed in microsecond, nanosecond, and even the picosecond.
It can perform millions of calculations in a few seconds as compared to man who will spend
many months to perform the same task.
Accuracy
In addition to being very fast, computers are very accurate.
The calculations are 100% error free.
Computers perform all jobs with 100% accuracy provided that the input is correct.
Storage Capability
Memory is a very important characteristic of c
omputers.
A computer has much more storage capacity than human beings.
It can store large amount of data.
It can store any type of data such as images, videos, text, audio, etc.
Diligence
Unlike human beings, a computer is free from monotony, tiredness, an
d lack of concentration.
It can work continuously without any error and boredom.
It can perform repeated tasks with the same speed and accuracy.
Versatility
A computer is a very versatile machine.
A computer is very flexible in performing the jobs to be do
ne.
This machine can be used to solve the problems related to various fields.
At one instance, it may be solving a complex scientific problem and the very next moment it
may be playing a card game.
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Reliability
A computer is a reliable machine.
Modern elect
ronic components have long lives.
Computers are designed to make maintenance easy.
Automation
Computer is an automatic machine.
Automation is the ability to perform a given task automatically. Once the computer receives a
program i.e., the program is store
d in the computer memory, then the program and instruction
can control the program execution without human interaction.
Reduction in Paper Work and Cost
The use of computers for data processing in an organization leads to reduction in paper work
and result
s in speeding up the process.
As data in electronic files can be retrieved as and when required, the problem of maintenance
of large number of paper files gets reduced.
Though the initial investment for installing a computer is high, it substantially reduc
es the cost
of each of its transaction.
Disadvantages of Computers
Following are certain disadvantages of computers.
No I.Q.
A computer is a machine that has no intelligence to perform any task.
Each instruction has to be given to the computer.
A computer
cannot take any decision on its own.
Dependency
It functions as per the user’s instruction, thus it is fully dependent on humans.
Environment
The operating environment of the computer should be dust free and suitable.
No Feeling
Computers have no feelings
or emotions.
It cannot make judgment based on feeling, taste, experience, and knowledge unlike humans.
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Computer
-
Applications
In this chapter, we will discuss the application of computers in various fields.
Business
A computer has high speed of calculat
ion, diligence, accuracy, reliability, or versatility
which has made it an integrated part in all business organizations.
Computer is used in business organizations for −
Payroll calculations
Budgeting
Sales analysis
Financial forecasting
Managing employee database
Maintenance of stocks, etc.
Banking
Today, banking is almost totally dependent on computers.
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Banks provide the
following facilities −
Online accounting facility, which includes checking current balance, making deposits and
overdrafts, checking interest charges, shares, and trustee records.
ATM machines which are completely automated are making it even easier for c
ustomers to
deal with banks.
Insurance
Insurance companies are keeping all records up
-
to
-
date with the help of computers.
Insurance companies, finance houses, and stock broking firms are widely using
computers for their concerns.
Insurance companies are
maintaining a database of all clients with information showing
−
Procedure to continue with policies
Starting date of the policies
Next due installment of a policy
Maturity date
Interests due
Survival benefits
Bonus
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Education
The computer helps in provid
ing a lot of facilities in the education system.
The computer provides a tool in the education system known as CBE (Computer Based
Education).
CBE involves control, delivery, and evaluation of learning.
Computer education is rapidly increasing the graph of
number of computer students.
There are a number of methods in which educational institutions can use a computer to
educate the students.
It is used to prepare a database about performance of a student and analysis is carried out
on this basis.
Marketing
I
n marketing, uses of the computer are following −
Advertising
− With computers, advertising professionals create art and graphics, write and
revise copy, and print and disseminate ads with the goal of selling more products.
Home Shopping
− Home shopping
has been made possible through the use of computerized
catalogues that provide access to product information and permit direct entry of orders to be
filled by the customers.
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Healthcare
Computers have become an important part in hospitals, labs, and dispens
aries. They
are being used in hospitals to keep the record of patients and medicines. It is also used
in scanning and diagnosing different diseases. ECG, EEG, ultrasounds and CT scans,
etc. are also done by computerized machines.
Following are some major f
ields of health care in which computers are used.
Diagnostic System
− Computers are used to collect data and identify the cause of illness.
Lab
-
diagnostic System
− All tests can be done and the reports are prepared by computer.
Patient Monitoring System
− These are used to check the patient's signs for abnormality
such as
in Cardiac Arrest, ECG, etc.
Pharma Information System
− Computer is used to check drug labels, expiry dates, harmful
side effects, etc.
Surgery
− Nowadays, computers are also used in performing surgery.
Engineering Design
Computers are widely used for En
gineering purpose.
One of the major areas is CAD (Computer Aided Design) that provides creation and
modification of images. Some of the fields are −
Structural Engineering
− Requires stress and strain analysis for design of ships, buildings,
budgets, air
planes, etc.
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Industrial Engineering
− Computers deal with design, implementation, and improvement of
integrated systems of people, materials, and equipment.
Architectural Engineering
− Computers help in planning towns, designing buildings,
determining a ra
nge of buildings on a site using both 2D and 3D drawings.
Military
Computers are largely used in defence. Modern tanks, missiles, weapons, etc. Military
also employs computerized control systems. Some military areas where a computer has
been used are −
M
issile Control
Military Communication
Military Operation and Planning
Smart Weapons
Communication
Communication is a way to convey a message, an idea, a picture, or speech that is
received and understood clearly and correctly by the person for whom it is m
eant. Some
main areas in this category are −
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E
-
mail
Chatting
Usenet
FTP
Telnet
Video
-
conferencing
Government
Computers play an important role in government services. Some major fields in this
category are −
Budgets
Sales tax department
Income tax depar
tment
Computation of male/female ratio
Computerization of voters lists
Computerization of PAN card
Weather forecasting
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Computer
–
Generations
Generation in computer terminology is a change in technology a computer is/was being
used. Initially, the genera
tion term was used to distinguish between varying hardware
technologies. Nowadays, generation includes both hardware and software, which
together make up an entire computer system.
There are five computer generations known till date. Each generation has be
en
discussed in detail along with their time period and characteristics. In the following table,
approximate dates against each generation has been mentioned, which are normally
accepted.
Following are the main five generations of computers.
S.No
Generatio
n & Description
1
First Generation
The period of first generation: 1946
-
1959. Vacuum tube based.
2
Second Generation
The period of second generation: 1959
-
1965. Transistor based.
3
Third Generation
The period of
third generation: 1965
-
1971. Integrated Circuit based.
4
Fourth Generation
The period of fourth generation: 1971
-
1980. VLSI microprocessor based.
5
Fifth Generation
The period of fifth generation: 1980
-
onwards. ULSI microprocessor based.
Computer
-
Types
Computers can be broadly classified by their speed an
d computing power.
S.No.
Type
Specifications
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1
PC (Personal
Computer)
It is a single user computer system having moderately powerful
microprocessor
2
Workstation
It is also a single user computer system, similar to personal
computer however has a more po
werful microprocessor.
3
Mini Computer
It is a multi
-
user computer system, capable of supporting
hundreds of users simultaneously.
4
Main Frame
It is a multi
-
user computer system, capable of supporting
hundreds of users simultaneously. Software technolog
y is
different from minicomputer.
5
Supercomputer
It is an extremely fast computer, which can execute hundreds of
millions of instructions per second.
PC (Personal Computer)
A PC can be defined as a small, relatively inexpensive computer designed for a
n
individual user. PCs are based on the microprocessor technology that enables
manufacturers to put an entire CPU on one chip. Businesses use personal computers
for word processing, accounting, desktop publishing, and for running spreadsheet and
database m
anagement applications. At home, the most popular use for personal
computers is playing games and surfing the Internet.
Although personal computers are designed as single
-
user systems, these systems are
normally linked together to form a network. In terms
of power, now
-
a
-
days high
-
end
models of the Macintosh and PC offer the same computing power and graphics capability
as low
-
end workstations by Sun Microsystems, Hewlett
-
Packard, and Dell.
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Workstation
Workstation is a computer used for engineering applica
tions (CAD/CAM), desktop
publishing, software development, and other such types of applications which require a
moderate amount of computing power and relatively high quality graphics capabilities.
Workstations generally come with a large, high
-
resolution
graphics screen, large amount
of RAM, inbuilt network support, and a graphical user interface. Most workstations also
have mass storage device such as a disk drive, but a special type of workstation, called
diskless workstation, comes without a disk drive.
Common operating systems for workstations are UNIX and Windows NT. Like PC,
workstations are also single
-
user computers like PC but are typically linked together to
form a local
-
area network, although they can also be used as stand
-
alone systems.
Minicomp
uter
It is a midsize multi
-
processing system capable of supporting up to 250 users
simultaneously.
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Mainframe
Mainframe is very large in size and is an expensive computer capable of supporting
hundreds or even thousands of users simultaneously. Mainframe
executes many
programs concurrently and supports many simultaneous execution of programs.
Supercomputer
Supercomputers are one of the fastest computers currently available. Supercomputers
are very expensive and are employed for specialized applications t
hat require immense
amount of mathematical calculations (number crunching).
For example, weather forecasting, scientific simulations, (animated) graphics, fluid
dynamic calculations, nuclear energy research, electronic design, and analysis of
geological
data (e.g. in petrochemical prospecting).
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Computer
-
Components
All types of computers follow the same basic logical structure and perform the following
five basic operations for converting raw input data into information useful to their users.
S.No.
Oper
ation
Description
1
Take Input
The process of entering data and instructions into the computer
system.
2
Store Data
Saving data and instructions so that they are available for
processing as and when required.
3
Processing
Data
Performing arithmetic, and
logical operations on data in order to
convert them into useful information.
4
Output
Information
The process of producing useful information or results for the user,
such as a printed report or visual display.
5
Control the
workflow
Directs the manner
and sequence in which all of the above
operations are performed.
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Input Unit
This unit contains devices with the help of which we enter data into the computer. This
unit creates a link between the user and the computer. The input devices translate the
in
formation into a form understandable by the computer.
CPU (Central Processing Unit)
CPU is considered as the brain of the computer. CPU performs all types of data
processing operations. It stores data, intermediate results, and instructions (program). It
c
ontrols the operation of all parts of the computer.
CPU itself has the following three components −
ALU (Arithmetic Logic Unit)
Memory Unit
Control Unit
Output Unit
The output unit consists of devices with the help of which we get the information from
the
computer. This unit is a link between the computer and the users. Output devices
translate the computer's output into a form understandable by the users.
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Computer
–
CPU (Central Processing Unit)
Central Processing Unit (CPU) consists of the following fea
tures −
CPU is considered as the brain of the computer.
CPU performs all types of data processing operations.
It stores data, intermediate results, and instructions (program).
It controls the operation of all parts of the computer.
CPU itself has followi
ng three components.
Memory or Storage Unit
Control Unit
ALU(Arithmetic Logic Unit)
Memory or Storage Unit
This unit can store instructions, data, and intermediate results. This unit supplies
information to other units of the computer when needed. It is
also known as internal
storage unit or the main memory or the primary storage or Random Access Memory
(RAM).
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Its size affects speed, power, and capability. Primary memory and secondary memory
are two types of memories in the computer. Functions of the memo
ry unit are −
It stores all the data and the instructions required for processing.
It stores intermediate results of processing.
It stores the final results of processing before these results are released to an output device.
All inputs and outputs are tra
nsmitted through the main memory.
Control Unit
This unit controls the operations of all parts of the computer but does not carry out any
actual data processing operations.
Functions of this unit are −
It is responsible for controlling the transfer of data
and instructions among other units of a
computer.
It manages and coordinates all the units of the computer.
It obtains the instructions from the memory, interprets them, and directs the operation of the
computer.
It communicates with Input/Output devices f
or transfer of data or results from storage.
It does not process or store data.
ALU (Arithmetic Logic Unit)
This unit consists of two subsections namely,
Arithmetic Section
Logic Section
Arithmetic Section
Function of arithmetic section is to perform arith
metic operations like addition,
subtraction, multiplication, and division. All complex operations are done by making
repetitive use of the above operations.
Logic Section
Function of logic section is to perform logic operations such as comparing, selecting
,
matching, and merging of data.
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Computer
-
Input Devices
Following are some of the important input devices which are used in a computer −
Keyboard
Mouse
Joy Stick
Light pen
Track Ball
Scanner
Graphic Tablet
Microphone
Magnetic Ink Card Reader(MICR)
Optical Character Reader(OCR)
Bar Code Reader
Optical Mark Reade
r(OMR)
Keyboard
Keyboard is the most common and very popular input device which helps to input data
to the computer. The layout of the keyboard is like that of traditional typewriter, although
there are some additional keys provided for performing addition
al functions.
Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys
or 108 keys are also available for Windows and Internet.
The keys on the keyboard are as follows −
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S.No
Keys & Description
1
Typing Keys
These keys include the letter keys (A
-
Z) and digit keys (09) which generally give the
same layout as that of typewriters.
2
Numeric Keypad
It is used to enter the numeric dat
a or cursor movement. Generally, it consists of a set
of 17 keys that are laid out in the same configuration used by most adding machines
and calculators.
3
Function Keys
The twelve function keys are present on the keyboard which are arranged in a row at
the top of the keyboard. Each function key has a unique meaning and is used for some
specific purpose.
4
Control keys
These keys provide cursor and screen control. It includes four directional arrow keys.
Control keys also include Home, End, Insert, Delet
e, Page Up, Page Down,
Control(Ctrl), Alternate(Alt), Escape(Esc).
5
Special Purpose Keys
Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock,
Num Lock, Space bar, Tab, and Print Screen.
Mouse
Mouse is the most popular pointi
ng device. It is a very famous cursor
-
control device
having a small palm size box with a round ball at its base, which senses the movement
of the mouse and sends corresponding signals to the CPU when the mouse buttons are
pressed.
Generally, it has two but
tons called the left and the right button and a wheel is present
between the buttons. A mouse can be used to control the position of the cursor on the
screen, but it cannot be used to enter text into the computer.
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Advantages
Easy to use
Not very expensiv
e
Moves the cursor faster than the arrow keys of the keyboard.
Joystick
Joystick is also a pointing device, which is used to move the cursor position on a monitor
screen. It is a stick having a spherical ball at its both lower and upper ends. The lower
sph
erical ball moves in a socket. The joystick can be moved in all four directions.
The function of the joystick is similar to that of a mouse. It is mainly used in Computer
Aided Designing (CAD) and playing computer games.
Light Pen
Light pen is a pointing
device similar to a pen. It is used to select a displayed menu item
or draw pictures on the monitor screen. It consists of a photocell and an optical system
placed in a small tube.
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When the tip of a light pen is moved over the monitor screen and the pen
button is
pressed, its photocell sensing element detects the screen location and sends the
corresponding signal to the CPU.
Track Ball
Track ball is an input device that is mostly used in notebook or laptop computer, instead
of a mouse. This is a ball whi
ch is half inserted and by moving fingers on the ball, the
pointer can be moved.
Since the whole device is not moved, a track ball requires less space than a mouse. A
track ball comes in various shapes like a ball, a button, or a square.
Scanner
Scanner
is an input device, which works more like a photocopy machine. It is used when
some information is available on paper and it is to be transferred to the hard disk of the
computer for further manipulation.
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Scanner captures images from the source which are
then converted into a digital form
that can be stored on the disk. These images can be edited before they are printed.
Digitizer
Digitizer is an input device which converts analog information into digital form. Digitizer
can convert a signal from the tele
vision or camera into a series of numbers that could be
stored in a computer. They can be used by the computer to create a picture of whatever
the camera had been pointed at.
Digitizer is also known as Tablet or Graphics Tablet as it converts graphics an
d pictorial
data into binary inputs. A graphic tablet as digitizer is used for fine works of drawing and
image manipulation applications.
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Microphone
Microphone is an input device to input sound that is then stored in a digital form.
The microphone is use
d for various applications such as adding sound to a multimedia
presentation or for mixing music.
Magnetic Ink Card Reader (MICR)
MICR input device is generally used in banks as there are large number of cheques to
be processed every day. The bank's code n
umber and cheque number are printed on
the cheques with a special type of ink that contains particles of magnetic material that
are machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main
advantages of MICR is
that it is fast and less error prone.
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Optical Character Reader (OCR)
OCR is an input device used to read a printed text.
OCR scans the text optically, character by character, converts them into a machine
readable code, and stores the text on the system
memory.
Bar Code Readers
Bar Code Reader is a device used for reading bar coded data (data in the form of light
and dark lines). Bar coded data is generally used in labelling goods, numbering the
books, etc. It may be a handheld scanner or may be embedded
in a stationary scanner.
Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which
is then fed to the computer that the bar code reader is connected to.
Optical Mark Reader (OMR)
OMR is a special type of optical scanner used t
o recognize the type of mark made by
pen or pencil. It is used where one out of a few alternatives is to be selected and marked.
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It is specially used for checking the answer sheets of examinations having multiple
choice questions.
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Computer
-
Output Devi
ces
Following are some of the important output devices used in a computer.
Monitors
Graphic Plotter
Printer
Monitors
Monitors, commonly called as
Visual Display Unit
(VDU), are the main output device of
a computer. It forms images from tiny dots, called p
ixels that are arranged in a
rectangular form. The sharpness of the image depends upon the number of pixels.
There are two kinds of viewing screen used for monitors.
Cathode
-
Ray Tube (CRT)
Flat
-
Panel Display
Cathode
-
Ray Tube (CRT) Monitor
The CRT display i
s made up of small picture elements called pixels. The smaller the
pixels, the better the image clarity or resolution. It takes more than one illuminated pixel
to form a whole character, such as the letter ‘e’ in the word help.
A finite number of charact
ers can be displayed on a screen at once. The screen can be
divided into a series of character boxes
-
fixed location on the screen where a standard
character can be placed. Most screens are capable of displaying 80 characters of data
horizontally and 25 l
ines vertically.
There are some disadvantages of CRT −
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Large in Size
High power consumption
Flat
-
Panel Display Monitor
The flat
-
panel display refers to a class of video devices that have reduced volume, weight
and power requirement in comparison to the CRT
. You can hang them on walls or wear
them on your wrists. Current uses of flat
-
panel displays include calculators, video games,
monitors, laptop computer, and graphics display.
The flat
-
panel display is divided into two categories −
Emissive Displays
− E
missive displays are devices that convert electrical energy into light.
For example, plasma panel and LED (Light
-
Emitting Diodes).
Non
-
Emissive Displays
− Non
-
emissive displays use optical effects to convert sunlight or
light from some other source into gr
aphics patterns. For example, LCD (Liquid
-
Crystal
Device).
Printers
Printer is an output device, which is used to print information on paper.
There are two types of printers −
Impact Printers
Non
-
Impact Printers
Impact Printers
Impact printers print the ch
aracters by striking them on the ribbon, which is then pressed
on the paper.
Characteristics of Impact Printers are the following −
Very low consumable costs
Very noisy
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Useful for bulk printing due to low cost
There is physical contact with the paper to pr
oduce an image
These printers are of two types −
Character printers
Line printers
Character Printers
Character printers are the printers which print one character at a time.
These are further divided into two types:
Dot Matrix Printer(DMP)
Daisy Wheel
Dot
Matrix Printer
In the market, one of the most popular printers is Dot Matrix Printer. These printers are
popular because of their ease of printing and economical price. Each character printed
is in the form of pattern of dots and head consists of a Matrix
of Pins of size (5*7, 7*9,
9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.
Advantages
Inexpensive
Widely Used
Other language characters can be printed
Disadvantages
Slow Speed
Poor Quality
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Daisy Wheel
Head is
lying on a wheel and pins corresponding to characters are like petals of Daisy
(flower) which is why it is called Daisy Wheel Printer. These printers are generally used
for word
-
processing in offices that require a few letters to be sent here and there wit
h
very nice quality.
Advantages
More reliable than DMP
Better quality
Fonts of character can be easily changed
Disadvantages
Slower than DMP
Noisy
More expensive than DMP
Line Printers
Line printers are the printers which print one line at a time.
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Thes
e are of two types −
Drum Printer
Chain Printer
Drum Printer
This printer is like a drum in shape hence it is called drum printer. The surface of the
drum is divided into a number of tracks. Total tracks are equal to the size of the paper,
i.e. for a paper
width of 132 characters, drum will have 132 tracks. A character set is
embossed on the track. Different character sets available in the market are 48 character
set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are
fast in
speed and can print 300 to 2000 lines per minute.
Advantages
Very high speed
Disadvantages
Very expensive
Characters fonts cannot be changed
Chain Printer
In this printer, a chain of character sets is used, hence it is called Chain Printer. A
standard char
acter set may have 48, 64, or 96 characters.
Advantages
Character fonts can easily be changed.
Different languages can be used with the same printer.
Disadvantages
Noisy
Non
-
impact Printers
Non
-
impact printers print the characters without using the ribbon.
These printers print a
complete page at a time, thus they are also called as Page Printers.
These printers are of two types −
Laser Printers
Inkjet Printers
Characteristics of Non
-
impact Printers
Faster than impact printers
They are not noisy
High quality
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Supports many fonts and different character size
Laser Printers
These are non
-
impact page pr
inters. They use laser lights to produce the dots needed
to form the characters to be printed on a page.
Advantages
Very high speed
Very high quality output
Good graphics quality
Supports many fonts and different character size
Disadvantages
Expensive
Ca
nnot be used to produce multiple copies of a document in a single printing
Inkjet Printers
Inkjet printers are non
-
impact character printers based on a relatively new technology.
They print characters by spraying small drops of ink onto paper. Inkjet print
ers produce
high quality output with presentable features.
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They make less noise because no hammering is done and these have many styles of
printing modes available. Color printing is also possible. Some models of Inkjet printers
can produce multiple copi
es of printing also.
Advantages
High quality printing
More reliable
Disadvantages
Expensive as the cost per page is high
Slow as compared to laser printer
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Computer
-
Memory
A memory is just like a human brain. It is used to store data and instructions. Co
mputer
memory is the storage space in the computer, where data is to be processed and
instructions required for processing are stored. The memory is divided into large number
of small parts called cells. Each location or cell has a unique address, which va
ries from
zero to memory size minus one. For example, if the computer has 64k words, then this
memory unit has 64 * 1024 = 65536 memory locations. The address of these locations
varies from 0 to 65535.
Memory is primarily of three types −
Cache Memory
Primary Memory/Main Memory
Secondary Memory
Cache Memory
Cache memory is a very high speed semiconductor memory which can speed up the
CPU. It acts as a buffer between the CPU and the main memory. It is use
d to hold those
parts of data and program which are most frequently used by the CPU. The parts of data
and programs are transferred from the disk to cache memory by the operating system,
from where the CPU can access them.
Advantages
The advantages of ca
che memory are as follows −
Cache memory is faster than main memory.
It consumes less access time as compared to main memory.
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It stores the program that can be executed within a short period of time.
It stores data for temporary use.
Disadvantages
The disa
dvantages of cache memory are as follows −
Cache memory has limited capacity.
It is very expensive.
Primary Memory (Main Memory)
Primary memory holds only those data and instructions on which the computer is
currently working. It has a limited capacity and
data is lost when power is switched off. It
is generally made up of semiconductor device. These memories are not as fast as
registers. The data and instruction required to be processed resides in the main memory.
It is divided into two subcategories RAM a
nd ROM.
Characteristics of Main Memory
These are semiconductor memories.
It is known as the main memory.
Usually volatile memory.
Data is lost in case power is switched off.
It is the working memory of the computer.
Faster than secondary memories.
A comp
uter cannot run without the primary memory.
Secondary Memory
This type of memory is also known as external memory or non
-
volatile. It is slower than
the main memory. These are used for storing data/information permanently. CPU directly
does not access thes
e memories, instead they are accessed via input
-
output routines.
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The contents of secondary memories are first transferred to the main memory, and then
the CPU can access it. For example, disk, CD
-
ROM, DVD, etc.
Characteristics of Secondary Memory
These a
re magnetic and optical memories.
It is known as the backup memory.
It is a non
-
volatile memory.
Data is permanently stored even if power is switched off.
It is used for storage of data in a computer.
Computer may run without the secondary memory.
Slower t
han primary memories.
Random Access Memory
RAM (Random Access Memory) is the internal memory of the CPU for storing data,
program, and program result. It is a read/write memory which stores data until the
machine is working. As soon as the machine is swi
tched off, data is erased.
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Access time in RAM is independent of the address, that is, each storage location inside
the memory is as easy to reach as other locations and takes the same amount of time.
Data in the RAM can be accessed randomly but it is ver
y expensive.
RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is
a power failure. Hence, a backup Uninterruptible Power System (UPS) is often used with
computer
s. RAM is small, both in terms of its physical size and in the amount of data it
can hold.
RAM is of two types −
Static RAM (SRAM)
Dynamic RAM (DRAM)
Static RAM (SRAM)
The word
static
indicates that the memory retains its contents as long as power is being
supplied. However, data is lost when the power gets down due to volatile nature. SRAM
chips use a matrix of 6
-
transistors and no capacitors. Transistors do not require power
to prevent leakage, so SRAM need not be refreshed on a regular basis.
There is ex
tra space in the matrix, hence SRAM uses more chips than DRAM for the
same amount of storage space, making the manufacturing costs higher. SRAM is thus
used as cache memory and has very fast access.
Characteristic of Static RAM
Long life
No need to refresh
Faster
Used as cache memory
Large size
Expensive
High power consumption
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Dynamic RAM (DRAM)
DRAM, unlike SRAM, must be continually
refreshed
in order to maintain the data. This
is done by placing the memory on a refresh circuit that rewrites the data sever
al hundred
times per second. DRAM is used for most system memory as it is cheap and small. All
DRAMs are made up of memory cells, which are composed of one capacitor and one
transistor.
Characteristics of Dynamic RAM
Short data lifetime
Needs to be refresh
ed continuously
Slower as compared to SRAM
Used as RAM
Smaller in size
Less expensive
Less power consumption
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Computer
-
Read Only Memory
ROM stands for
Read Only Memory
. The memory from which we can only read but
cannot write on it. This type of memory is
non
-
volatile. The information is stored
permanently in such memories during manufacture. A ROM stores such instructions that
are required to start a computer. This operation is referred to as
bootstrap
. ROM chips
are not only used in the computer but also
in other electronic items like washing machine
and microwave oven.
Let us now discuss the various types of ROMs and their characteristics.
MROM (Masked ROM)
The very first ROMs were hard
-
wired devices that contained a pre
-
programmed set of
data or instr
uctions. These kind of ROMs are known as masked ROMs, which are
inexpensive.
PROM (Programmable Read Only Memory)
PROM is read
-
only memory that can be modified only once by a user. The user buys a
blank PROM and enters the desired contents using a PROM pro
gram. Inside the PROM
chip, there are small fuses which are burnt open during programming. It can be
programmed only once and is not erasable.
EPROM (Erasable and Programmable Read Only
Memory)
EPROM can be erased by exposing it to ultra
-
violet light for a
duration of up to 40
minutes. Usually, an EPROM eraser achieves this function. During programming, an
electrical charge is trapped in an insulated gate region. The charge is retained for more
than 10 years because the charge has no leakage path. For erasi
ng this charge, ultra
-
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violet light is passed through a quartz crystal window (lid). This exposure to ultra
-
violet
light dissipates the charge. During normal use, the quartz lid is sealed with a sticker.
EEPROM (Electrically Erasable and Programmable Read
O
nly Memory)
EEPROM is programmed and erased electrically. It can be erased and reprogrammed
about ten thousand times. Both erasing and programming take about 4 to 10 ms
(millisecond). In EEPROM, any location can be selectively erased and programmed.
EEPROM
s can be erased one byte at a time, rather than erasing the entire chip. Hence,
the process of reprogramming is flexible but slow.
Advantages of ROM
The advantages of ROM are as follows −
Non
-
volatile in nature
Cannot be accidentally changed
Cheaper than R
AMs
Easy to test
More reliable than RAMs
Static and do not require refreshing
Contents are always known and can be verified
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Computer
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Motherboard
The motherboard serves as a single platform to connect all of the parts of a computer
together. It connects
the CPU, memory, hard drives, optical drives, video card, sound
card, and other ports and expansion cards directly or via cables. It can be considered as
the backbone of a computer.
Features of Motherboard
A motherboard comes with following features −
Motherboard varies greatly in supporting various types of components.
Motherboard supports a single type of CPU and few types of memories.
Video cards, hard disks, sound cards have to be compatible with the mot
herboard to function
properly.
Motherboards, cases, and power supplies must be compatible to work properly together.
Popular Manufacturers
Following are the popular manufacturers of the motherboard.
Intel
ASUS
AOpen
ABIT
Biostar
Gigabyte
MSI
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Description of
Motherboard
The motherboard is mounted inside the case and is securely attached via small screws
through pre
-
drilled holes. Motherboard contains ports to connect all of the internal
components. It provides a single socket for CPU, whereas for memory, norm
ally one or
more slots are available. Motherboards provide ports to attach the floppy drive, hard
drive, and optical drives via ribbon cables. Motherboard carries fans and a special port
designed for power supply.
There is a peripheral card slot in front o
f the motherboard using which video cards, sound
cards, and other expansion cards can be connected to the motherboard.
On the left side, motherboards carry a number of ports to connect the monitor, printer,
mouse, keyboard, speaker, and network cables. Mot
herboards also provide USB ports,
which allow compatible devices to be connected in plug
-
in/plug
-
out fashion. For
example, pen drive, digital cameras, etc.
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Computer
-
Memory Units
Memory unit is the amount of data that can be stored in the storage unit.
This storage
capacity is expressed in terms of Bytes.
The following table explains the main memory storage units −
S.No.
Unit & Description
1
Bit (Binary Digit)
A binary digit is logical 0 and 1 representing a passive or an active state of a component
in an electric circuit.
2
Nibble
A group of 4 bits is ca
lled nibble.
3
Byte
A group of 8 bits is called byte. A byte is the smallest unit, which can represent a data
item or a character.
4
Word
A computer word, like a byte, is a group of fixed number of bits processed as a unit,
which varies from computer to
computer but is fixed for each computer.
The length of a computer word is called word
-
size or word length. It may be as small
as 8 bits or may be as long as 96 bits. A computer stores the information in the form
of computer words.
The following table list
s some higher storage units −
S.No.
Unit & Description
1
Kilobyte (KB)
1 KB = 1024 Bytes
2
Megabyte (MB)
1 MB = 1024 KB
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3
GigaByte (GB)
1 GB = 1024 MB
4
TeraByte (TB)
1 TB = 1024 GB
5
PetaByte (PB)
1 PB = 1024 TB
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Computer
-
Ports
A port is a physic
al docking point using which an external device can be connected to
the computer. It can also be programmatic docking point through which information flows
from a program to the computer or over the Internet.
Characteristics of Ports
A port has the followi
ng characteristics −
External devices are connected to a computer using cables and ports.
Ports are slots on the motherboard into which a cable of external device is plugged in.
Examples of external devices attached via ports are the mouse, keyboard, monit
or,
microphone, speakers, etc.
Let us now discuss a few important types of ports −
Serial Port
Used for external modems and older computer mouse
Two versions: 9 pin, 25 pin model
Data travels at 115 kilobits per second
Parallel Port
Used for scanners and
printers
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Also called printer port
25 pin model
IEEE 1284
-
compliant Centronics port
PS/2 Port
Used for old computer keyboard and mouse
Also called mouse port
Most of the old computers provide two PS/2 port, each for the mouse and keyboard
IEEE 1284
-
complia
nt Centronics port
Universal Serial Bus (or USB) Port
It can connect all kinds of external USB devices such as external hard disk, printer, scanner,
mouse, keyboard, etc.
It was introduced in 1997.
Most of the computers provide two USB ports as minimum.
Da
ta travels at 12 megabits per seconds.
USB compliant devices can get power from a USB port.
VGA Port
Connects monitor to a computer's video card.
It has 15 holes.
Similar to the serial port connector. However, serial port connector has pins, VGA port has
h
oles.
Power Connector
Three
-
pronged plug.
Connects to the computer's power cable that plugs into a power bar or wall socket.
Firewire Port
Transfers large amount of data at very fast speed.
Connects camcorders and video equipment to the computer.
Data trav
els at 400 to 800 megabits per seconds.
Invented by Apple.
It has three variants: 4
-
Pin FireWire 400 connector, 6
-
Pin FireWire 400 connector, and 9
-
Pin
FireWire 800 connector.
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Modem Port
Connects a PC's modem to the telephone network.
Ethernet Port
Connect
s to a network and high speed Internet.
Connects the network cable to a computer.
This port resides on an Ethernet Card.
Data travels at 10 megabits to 1000 megabits per seconds depending upon the network
bandwidth.
Game Port
Connect a joystick to a PC
Now
replaced by USB
Digital Video Interface, DVI port
Connects Flat panel LCD monitor to the computer's high
-
end video graphic cards.
Very popular among video card manufacturers.
Sockets
Sockets connect the microphone and speakers to the sound card of the com
puter.
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Computer
-
Hardware
Hardware represents the physical and tangible components of a computer, i.e. the
components that can be seen and touched.
Examples of Hardware are the following −
Input devices
− keyboard, mouse, etc.
Output devices
− printer, monitor, etc.
Sec
ondary storage devices
− Hard disk, CD, DVD, etc.
Internal components
− CPU, motherboard, RAM, etc.
Rela
tionship between Hardware and Software
Hardware and software are mutually dependent on each other. Both of them must work
together to make a computer produce a useful output.
Software cannot be utilized without supporting hardware.
Hardware without a set o
f programs to operate upon cannot be utilized and is useless.
To get a particular job done on the computer, relevant software should be loaded into the
hardware.
Hardware is a one
-
time expense.
Software development is very expensive and is a continuing exp
ense.
Different software applications can be loaded on a hardware to run different jobs.
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A software acts as an interface between the user and the hardware.
If the hardware is the 'heart' of a computer system, then the software is its 'soul'. Both are
compl
ementary to each other.
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Computer
-
Software
Software is a set of programs, which is designed to perform a well
-
defined function. A
program is a sequence of instructions written to solve a particular problem.
There are two types of software −
System Softw
are
Application Software
System Software
The system software is a collection of programs designed to operate, control, and extend
the processing capabilities of the computer itself. System software is generally prepared
by the computer manufacturers. These software products comprise of programs w
ritten
in low
-
level languages, which interact with the hardware at a very basic level. System
software serves as the interface between the hardware and the end users.
Some examples of system software are Operating System, Compilers, Interpreter,
Assemblers
, etc.
Here is a list of some of the most prominent features of a system software −
Close to the system
Fast in speed
D
ifficult to design
Difficult to understand
Less interactive
Smaller in size
Difficult to manipulate
Generally written in low
-
level language
Application Software
Application software products are designed to satisfy a particular need of a particular
environ
ment. All software applications prepared in the computer lab can come under the
category of Application software.
Application software may consist of a single program, such as Microsoft's notepad for
writing and editing a simple text. It may also consist o
f a collection of programs, often
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called a software package, which work together to accomplish a task, such as a
spreadsheet package.
Examples of Application software are the following −
Payroll Software
Student Record Software
Inventory Management Softwar
e
Income Tax Software
Railways Reservation Software
Microsoft Office Suite Software
Microsoft Word
Microsoft Excel
Microsoft PowerPoint
Features of application software are as follows −
Close to the user
Easy to design
More interactive
Slow in speed
Generally written in high
-
level language
Easy to understand
Easy to manipulate and use
Bigger in size and requires large storage space
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Computer
-
Data and Information
Data
can be defined as a representation of facts, concepts, or instructions in a formalized
manner, which should be suitable for communication, interpretation, or processing by
human or electronic machine.
Data is represented with the help of characters such as
alphabets (A
-
Z, a
-
z), digits (0
-
9)
or special characters (+,
-
,/,*,<,>,= etc.)
What is Information?
Information
is organized or classified data, which has some meaningful values for the
receiver. Information is the processed data on which decisions and act
ions are based.
For the decision to be meaningful, the processed data must qualify for the following
characteristics −
Timely
− Information should be available when required.
Accuracy
− Information should be accurate.
Completeness
− Information should be c
omplete.
Data Processing Cycle
Data processing is the re
-
structuring or re
-
ordering of data by people or machine to
increase their usefulness and add values
for a particular purpose. Data processing
consists of the following basic steps
-
input, processing, and output. These three steps
constitute the data processing cycle.
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Input
− In this step, the input data is prepared in some convenient form for processing. The
form will depend on the processing machine. For example, when electronic computers are
used, the input data can be recorded on any one
of the several types of input medium, such
as magnetic disks, tapes, and so on.
Processing
− In this step, the input data is changed to produce data in a more useful form.
For example, pay
-
checks can be calculated from the time cards, or a summary of sales
for
the month can be calculated from the sales orders.
Output
− At this stage, the result of the proceeding processing step is collected. The particular
form of the output data depends on the use of the data. For example, output data may be
pay
-
checks for
employees.
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Computer
-
Networking
A
computer network
is a system in which multiple computers are connected to each
other to share information and resources.
Characteristics of a Computer Network
Share resources from one computer to another.
Create files and store them
in one computer, access those files from the other computer(s)
connected over the network.
Connect a printer, scanner, or a fax machine to one computer within the network and let other
computers of the network use the machines available over the network.
F
ollowing is the list of hardware's required to set up a computer network.
Network Cables
Distributors
Routers
Internal Network Cards
External Network Cards
Network Cables
Network cables are used to connect computers. The most commonly used cable is
Categor
y 5 cable RJ
-
45.
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Distributors
A computer can be connected to another one via a serial port but if we need to connect
many computers to produc
e a network, this serial connection will not work.
The solution is to use a central body to which other computers, printers, scanners, etc.
can be connected and then this body will manage or distribute network traffic.
Router
A router is a type of device which acts as the central point among computers and other
devices that are a part of the network. It is equipped with holes called ports. Computers
and other devices are connected to a router using network cables. Now
-
a
-
days ro
uter
comes in wireless modes using which computers can be connected without any physical
cable.
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Network Card
Network card is a necessary com
ponent of a computer without which a computer cannot
be connected over a network. It is also known as the network adapter or Network
Interface Card (NIC). Most branded computers have network card pre
-
installed. Network
cards are of two types: Internal and
External Network Cards.
Internal Network Cards
Motherboard has a slot for internal network card where it is to be inserted. Internal
network cards are of two types in which the first type uses Peripheral Component
Interconnect (PCI) connection, while the s
econd type uses Industry Standard
Architecture (ISA). Network cables are required to provide network access.
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External Network Cards
External ne
twork cards are of two types: Wireless and USB based. Wireless network
card needs to be inserted into the motherboard, however no network cable is required
to connect to the network.
Universal Serial Bus (USB)
USB card is easy to use and connects via USB port. Computers automatically detect
USB card and can install the drivers required to support the USB network card
automatically.
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Computer
-
Operating System
The Operating System is a program with the following features −
An operating system is a program that acts as an in
terface between the software and the
computer hardware.
It is an integrated set of specialized programs used to manage overall resources and
operations of the computer.
It is a specialized software that controls and monitors the execution of all other prog
rams that
reside in the computer, including application programs and other system software.
Objectives of Operating System
The objectives of the operating system are −
To make the computer system convenient to use in an efficient manner.
To hide the details of the hardware resources from the users.
To provide users a convenient interface to use the computer system.
To act as a
n intermediary between the hardware and its users, making it easier for the users
to access and use other resources.
To manage the resources of a computer system.
To keep track of who is using which resource, granting resource requests, and mediating
confl
icting requests from different programs and users.
To provide efficient and fair sharing of resources among users and programs.
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Characteristics of Operating System
Here is a list of some of the most prominent characteristic features of Operating Systems
−
Memory Management
− Keeps track of the primary memory, i.e. what part of it is in use by
whom, what part is not in use, etc. and allocates the memory when a process or program
requests it.
Processor Management
− Allocates the processor (CPU) to a process and deallocates the
processor when it is no longer required.
Device Management
− Keeps track of all the devices. This is also called I/O controller that
decides which process gets the device, when, and for how m
uch time.
File Management
− Allocates and de
-
allocates the resources and decides who gets the
resources.
Security
− Prevents unauthorized access to programs and data by means of passwords and
other similar techniques.
Job Accounting
− Keeps track of time a
nd resources used by various jobs and/or users.
Control Over System Performance
− Records delays between the request for a service and
from the system.
Interaction with the Operators
− Interaction may take place via the console of the computer
in the form
of instructions. The Operating System acknowledges the same, does the
corresponding action, and informs the operation by a display screen.
Error
-
detecting Aids
− Production of dumps, traces, error messages, and other debugging
and error
-
detecting methods.
Coordination Between Other Software and Users
− Coordination and assignment of
compilers, interpreters, assemblers, and other software to the various users of the computer
systems.
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Computer
-
Internet and Intranet
In this chapter, we will see what is Internet and Intranet, as well as discuss the similarities
and differences between the two.
Internet
It is a worldwide/global system of interconnected computer networks. It uses the
standard Internet Protocol (TCP/IP).
Every computer in Internet is identified by a unique
IP address. IP Address is a unique set of numbers (such as 110.22.33.114) which
identifies a computer’s location.
A special computer DNS (Domain Name Server) is used to provide a name to the IP
Address s
o that the user can locate a computer by a name. For example, a DNS server
will resolve a name
https://www.tutorialspoint.com
to a particular IP address to uniquely
identify the computer on which
this website is hosted.
Internet is accessible to every user all over the world.
Intranet
Intranet is the system in which multiple PCs are connected to each other. PCs in intranet
are not available to the world outside the intranet. Usually each organization has its own
Intranet network and members/employees of that organization can access the
computers in their intranet.
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Each computer in Intranet is also identified by an IP Address which is unique among the
computers in that Intranet.
Si
milarities between Internet and Intranet
Intranet uses the internet protocols such as TCP/IP and FTP.
Intranet sites are accessible via the web browser in a similar way as websites in the internet.
However, only members of Intranet network can access intra
net hosted sites.
In Intranet, own instant messengers can be used as similar to yahoo messenger/gtalk over
the internet.
Differences between Internet and Intranet
Internet is general to PCs all over the world whereas Intranet is specific to few PCs.
Internet provides a wider and better access to websites to a large population, whereas Intranet
is restricted.
Internet is not as safe as Intranet. Intranet can be safely privatized as per the need.
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How to Buy a Computer?
In this chapter, we will supply
relevant information to help you buy a desktop on
component by component basis. As desktops are highly customizable, so it is better to
learn about the main parts and then visit the manufacturer or the retailer shop or site,
instead of just looking at some
specific model directly.
Popular desktop brands are Dell, Lenovo, HP and Apple. Always compare the desktops
based on their specifications and base price.
Monitor
Size
− It is the diagonal size of the LCD screen. Larger the area, bigger the picture screen. A
bigger picture is preferable for movie watching and gaming. It will increase the productivity as
well.
Resolution
− This is the number of pixels on the screen. For example, 24inch display is
1920x1200 (width by length) and 22
-
inch display is 1680x1050. High resolution provides
better picture quality and a nice gaming experience.
Inputs
− Now
-
a
-
days monitors
can accept inputs from cable as well apart from the computer.
They can also have USB ports.
Stand
− Some monitors come with adjustable stands while some may not.
Recommended
− 24 Inch LCD.
Operating System
Operating System is the main software of the comp
uter as everything will run on it in one form
or other.
There are primarily three choices:
Windows, Linux, Apple OS X.
Linux
is free, however people generally do not use it for home purpose.
Apple OS X
works only on Apple desktops.
Windows 7
is very popular among desktop users.
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Most of the computers come pre
-
equipped with Windows 7 Starter edition.
Windows 8
is recently introduced and is available in the market.
Windows 7 and Windows 8
come in multiple versions from starter, home basic, home
p
remium, professional, ultimate, and enterprise editions.
As the edition version increases, their features list and price increases.
Recommended
− Windows 7 Home Premium.
Optical Drive (CD / DVD / Blu
-
ray)
Optical drive is the drive on a computer, which is responsible for using CD, DVD, and Blu
-
ray
discs.
Now
-
a
-
days, DVD burners are industry standards.
DVD Burner
can burn CD, DVD and play them.
DVD Burner is cheaper than Blu
-
ray drives.
Blu
-
ray drives can play HD movies but are costlier component.
Recommended
− DVD Burner.
Memory
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RAM is considered as Computer Memory as
the performance of a computer is directly
proportional to its memory and processor.
Today's software and operating system require high memory.
Today commonly used RAM is DDR3, which operates at 1066Mhz.
As per Windows 7, 1 GB is the minimum RAM required to
function properly.
Recommended
− 4 GB.
Hard Drive
Hard disk is used for storage purpose. Higher the capacity, more data you can save in it.
Now
-
a
-
days computers are equipped with 500GB hard drive, w
hich can be extended to 2TB.
Most hard drives in desktop operate at the standard performance speed of 7200RPM.
Recommended
− 500GB.
CPU
Frequency (GHz)
− This determines the speed of the processor. More the speed, better the
CPU.
Cores
− Now
-
a
-
days CPUs come with more than one core, which is like having more than
one CPU in the computer. Programs which can take advantag
e of multi
-
core environment will
run faster on such machines.
Brand
− Intel or AMD. Both are equivalent. Intel is in lead.
Cache
− Higher the L1, L2 cache, better the CPU performance.
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Recommended
− Intel Core i3
-
3225 3.30 GHz Processor.